Reversible planetary gear assembly

ABSTRACT

A planetary gear assembly includes a ring gear configured for connection to a rotor of an electric motor when in a first position and configured for connection to a housing of the electric motor when in a second position, a sun gear configured for connection to the housing when the ring gear is in the first position and configured for connection to the rotor when the ring gear is in the second position, and a plurality of planet gears configured to mesh with the ring gear and the sun gear.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. provisional patentapplication No. 61/261,635, filed Nov. 16, 2009, the contents of whichare incorporated herein by reference.

FIELD

The present application relates to the field of mechanical powertransmission, and more particularly to planetary gear assemblies,including planetary gear assemblies used in vehicles.

BACKGROUND

A planetary gear assembly converts an input rotation to an outputrotation. Typically, a gear ratio of the planetary gear assembly isconfigured such that the output rotation has a different angularvelocity and torque than the input rotation. In one application, aplanetary gear assembly is coupled to the rotational output of anelectric motor. The planetary gear assembly may be used to convert therotational output of the electric motor to a rotational output havingtorque and angular velocity characteristics suitable for the particularapplication.

The typical planetary gear assembly includes a sun gear, numerous planetgears, and a ring gear. The sun gear has a toothed exterior peripheryand defines a central axis. The planet gears each have a toothedexterior periphery that is configured to mesh with the toothed exteriorperiphery of the sun gear. The ring gear, which is sometimes referred toas an annulus, has a toothed interior periphery that is configured tomesh with the toothed exterior periphery of the planet gears. The ringgear has a central axis, which is coaxial with the central axis of thesun gear. Some planetary gear assemblies also include a carrier, whichis connected to each of the planet gears. The carrier also defines acentral axis, which is coaxial with the central axis of the sun gear.

Operation of a planetary gear assembly that includes a planet gearcarrier involves (i) fixing the position of one of the ring gear, thecarrier, and the sun gear; (ii) rotating another one of the ring gear,the carrier, and the sun gear; and (iii) generating a rotational outputat the remaining one of the ring gear, the carrier, and the sun gear.For example, in one configuration, the ring gear is maintained in afixed position, the sun gear receives an input rotation, and an outputrotation is generated at the planet carrier, which rotates about itscentral axis.

In general, planetary gear assemblies are designed and machined tointroduce a particular gear ratio between the input rotation and theoutput rotation. Therefore, most planetary gear assemblies areapplication specific devices. In view of the foregoing, it would bedesirable to utilize a particular planetary gear assembly in multipleapplications. However, parameters such as input angular velocity, inputtorque, output angular velocity, output torque, and maximum operatingspeed, often restrict the potential use of a planetary gear assembly toonly a limited number of applications. In addition, the continuingdesire to increase the efficiency of electric products makes itdesirable for electric motors and planetary gear assemblies to generatemore output torque with a system that occupies less space. Accordingly,further advancements are desirable for planetary gear assemblies.

SUMMARY

A reversible planetary gear assembly has been developed. The planetarygear assembly includes a ring gear configured for connection to a rotorof an electric motor when in a first position and configured forconnection to a housing of the electric motor when in a second position,a sun gear configured for connection to the housing when the ring gearis in the first position and configured for connection to the rotor whenthe ring gear is in the second position, and a plurality of planet gearsconfigured to mesh with the ring gear and the sun gear.

According to another embodiment of the present disclosure an electricmotor assembly has been developed that includes a housing, a statorpositioned within the housing, a rotor positioned within the housing andconfigured to rotate relative to the stator; and a planetary gearassembly associated with the rotor, the planetary gear assemblycomprising a ring gear, a sun gear, and a plurality of planet gearsconfigured to engage meshingly the ring gear and the sun gear, whereinthe planetary gear assembly is configured for positioning in a firstorientation in which the rotor rotates an output member of the planetarygear assembly with a first gear ratio and in a second orientation inwhich the rotor rotates the output member of the planetary gear assemblywith a second gear ratio.

A method has been developed for arranging a gear train relative to aninput torque member. The method includes providing a planetary gearassembly comprising a ring gear, a sun gear, a plurality of planetgears, and a carrier for the planet gears, wherein at least two of thering gear, sun gear, and carrier are configured to be connected to theinput torque member such that a plurality of planetary gearconfigurations are possible for the planetary gear assembly, selectingone of the plurality of planetary gear configurations for the planetarygear assembly, and arranging the planetary gear assembly relative to theinput torque member in the selected one of the plurality of planetarygear configurations.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block diagram illustrating a vehicle including a chassis, atraction member, and a drive system;

FIG. 2 is side perspective view illustrating a portion of the vehicle ofFIG. 1;

FIG. 3 is a block diagram of the drive system of FIG. 1, including aspeed controller and an electric motor assembly;

FIG. 4 is a cross sectional view of the electric motor assembly of FIG.3, having a planetary gear assembly oriented in a first position and anoutput shaft connected to a carrier of the planetary gear assembly;

FIG. 5 is an enlarged cross sectional view of the planetary gearassembly of FIG. 4;

FIG. 6 is a top perspective view of planet gears and the carrier of theplanetary gear assembly of FIG. 4;

FIG. 7 is top perspective view of the carrier of FIG. 6 shown withoutthe planet gears;

FIG. 8 is a bottom perspective view of the carrier of FIG. 6, shownwithout the planet gears;

FIG. 9 is a cross sectional view of the electric motor assembly of FIG.3, having the planetary gear assembly of FIG. 4 oriented in a secondposition, the output shaft remains connected to the carrier of theplanetary gear assembly;

FIG. 10 is a flowchart depicting an exemplary method of operating theelectric motor assembly of FIG. 3;

FIG. 11 is a cross sectional view of the electric motor assembly of FIG.3, having the planetary gear assembly of FIG. 4 oriented in the firstposition and having an output shaft connected to a sun gear of theplanetary gear assembly;

FIG. 12 is a cross sectional view of the electric motor assembly of FIG.3, having the planetary gear assembly of FIG. 4 oriented in the secondposition and having an output shaft connected to a ring gear of theplanetary gear assembly;

FIG. 13 is a side perspective view illustrating a portion of the vehicleof FIG. 1, the electric motor assembly of FIG. 3 being in a tractionmotor configuration;

FIG. 14 is a block diagram illustrating an alternative embodiment of thevehicle of FIG. 1, which includes numerous drive systems and tractionmembers; and

FIG. 15 is a rear perspective view illustrating an alternativeembodiment of the vehicle of FIG. 1, the vehicle being a watercraft.

DETAILED DESCRIPTION

As shown in FIG. 1, a vehicle 100 includes a traction member 104connected to a drive system 108 and positioned in a chassis 112. Thevehicle 100 is a ground traversing vehicle such as a car, light dutytruck, commercial duty truck (tractor trailer), golf cart, motorcycle,all-terrain vehicle, or the like. The chassis 112 provides a framework,which supports and positions the drive system 108 and the tractionmember 104. Accordingly, depending on the type of vehicle 100, thechassis 112 may be formed from metal, fiberglass, and/or other types ofsuitable materials.

As shown in FIG. 2, in at least one embodiment the traction member 104includes a wheel 116 and a tire 120. The traction member 104 ismechanically coupled to the drive system 108 by an axle 124. The axle124 transmits a rotational force generated by the drive system 108 intoa traction force that moves the vehicle 100. Rotation of the axle 124rotates the wheel 116 and the tire 120. The vehicle 100 may includemultiple wheels 116 and tires 120 to support the chassis 112; however,for simplicity, only one wheel and one tire are illustrated in FIG. 2.

As shown in FIG. 3, the drive system 108 includes an electric motorassembly 128 electrically coupled to a speed controller 132. Theelectric motor assembly 128 generates a drive torque that is coupled tothe traction member 104 to move the vehicle 100. The speed controller132 controls the torque generated by the electric motor assembly 128,such that the speed of the vehicle 100 may be controlled. The speedcontroller 132 may be any type of electronic controller configured tocontrol an output torque and/or the angular velocity of an electricmotor, as known to those of ordinary skill in the art.

As shown in FIG. 4, the electric motor assembly 128 includes a stator136, a rotor 140, and a planetary gear assembly 144, each at leastpartially positioned within a housing 148. The planetary gear assembly144 is shown being connected to a shaft 146 (shown in phantom), whichmay be the axle 124 (FIG. 2). The housing 148 is typically a metalcasing, such as a steel casing or a cast aluminum casing. The housing148, however, could also be comprised of any other suitable material.The housing 148 includes a bowl portion 152 connected to a cover plateportion 156. Together, the bowl 152 and the cover plate 156 define ahousing internal space in which the stator 136, the rotor 140, and theplanetary gear assembly 144 are at least partially positioned. Thehousing internal space includes the volume bounded by the opposite endsof the housing 148, as noted by dashed lines A and B.

The bowl 152 of the housing 148 defines a seat 164 configured to receivea left bearing 168. The bowl 152 may also include an opening (not shown)to enable an electrical connector 172 to extend through the bowl andinto the housing internal space.

The cover plate 156, as shown in FIG. 4, connects to the bowl 152 of thehousing 148 with numerous fasteners 176. The cover plate 156 may beremoved from the bowl 152 to enable adjustment and configuration of thestator 136, the rotor 140, and the planetary gear assembly 144. Thecover plate 156, along with a portion of the rotor 140, defines anotherseat 178 configured to receive a right bearing 180. Additionally, thecover plate 156 portion of the housing 148 defines an opening 184configured to receive and to support a portion of the planetary gearassembly 144. The center opening 184 in the housing 148 includes asplined portion having numerous splines 188 or other such connectionmembers, which are configured to mesh with a corresponding set ofsplines or other such connection members formed on the portion of theplanetary gear assembly 144 received by the opening 184.

In another embodiment (not shown in the figures), the electric motorassembly 128 includes a housing having a three-piece configuration. Thethree-piece housing includes a first end cap and a second end capconnected to a generally cylindrical body portion. The first end cap issimilar or identical to the cover plate 156. The second end cap definesa seat to support the left bearing 168. The stator 136, the rotor 140,and the planetary gear assembly 144 are at least partially positionedwithin the body portion.

With continued reference to FIG. 4, the stator 136 is positionedcompletely within the housing internal space (Lines A and B). The stator136 includes a core 200 and a winding 204 extending through the core. Aleft set of end turns 208 of the winding 204 extends from the left sideof the core 200, and a right set of end turns 212 of the winding extendsfrom the right side of the core. An axial length of the stator 136 maybe defined as the distance between the tips of the left and the rightend turns 208, 212 as measured in direction 288 (FIG. 4). The stator 136defines a stator internal space in which the rotor 140 and the planetarygear assembly 144 are at least partially positioned. The stator internalspace includes the volume bounded by the left and the right end turns208, 212, as noted by dashed lines C and D of FIG. 4.

The rotor 140 is positioned completely within the housing internal space(Lines A and B) and is positioned at least partially within the statorinternal space (Lines C and D). The rotor 140 is configured to rotaterelative to the housing and the stator 136 about the left and the rightbearings 168, 180. The rotor 140 may be referred to as an input torquemember of the planetary gear assembly 144, because it provides theplanetary gear assembly with an input rotation. The rotor 140 includespermanent magnets 192 connected to a support frame 196. The permanentmagnets 192 are positioned in close proximity to the core 200 of thestator 136. The frame 196 of the rotor 140 defines an opening 224configured to receive a portion of the planetary gear assembly 144. Theopening 224 in the rotor 140 includes a splined portion having numeroussplines 228 or other such connection members, which are configured tomesh with a corresponding set of splines or other such connectionmembers formed on the portion of the planetary gear assembly 144received by the opening. The rotor 140 defines a rotor internal space inwhich the planetary gear assembly 144 is at least partially positioned.The rotor internal space includes the volume bounded by the lateral endsof the rotor 140, as noted by dashed lines E and F. The opening 224 inthe rotor 140 is positioned within the rotor internal space.

As shown in FIG. 5 the planetary gear assembly 144 includes a ring gear232, a sun gear 236, a carrier 240, and numerous planet gears 244connected to the carrier. Each of the ring gear 232, the sun gear 236,the carrier 240, and the planet gears 244 are formed from metal such assteel, or the like. The ring gear 232, which has a circular periphery,includes a toothed portion 248 and a connection portion 252. The toothedportion 248 includes numerous teeth, or the like, which are configuredto engage meshingly corresponding teeth of the planet gears 244. Theconnection portion 252 is a splined portion having numerous splines 256or other such connection members, which are configured to mesh with thesplines 188 formed within the opening 224 of the rotor 140 (as shown inFIG. 4). When the connection portion 252 of the ring gear 232 isreceived by the opening 224 in the rotor 140, the ring gear rotates withthe rotor and the torque generated by the rotor is transferred to thering gear. The ring gear 232 defines an internal cavity 260 in which atleast a portion of the carrier 240 is positioned.

With continued reference to FIG. 5, the sun gear 236 has a generallycircular periphery and includes a toothed portion 264 and a connectionportion 268. The toothed portion 264 includes numerous teeth, or thelike, which are configured to engage meshingly corresponding teeth ofthe planet gears 244. The connection portion 268 of the sun gear 236 isa splined portion having numerous splines 272 or other such connectionmembers, which are configured to mesh with the splines 188 formed withinthe opening 184 of the housing 148 (as shown in FIG. 4). When theconnection portion 268 of the sun gear 236 is received by the opening184 in the housing 148, the sun gear is fixedly connected to the housingsuch that the sun gear does not rotate relative to the housing. The sungear 236 defines an internal cavity 276 in which at least a portion ofthe carrier 240 is positioned.

As shown in FIG. 6, the planet gears 244 have a toothed exterior surfaceconfigured to rotate about a non-rotatable central post 286. The toothedsurface is configured to engage meshingly the toothed portion 248 of thering gear 232 and the toothed portion 264 of the sun gear 236 (as shownin FIG. 5). The planetary gear assembly 144 may include six planet gears244, grouped into three clusters each separated by approximately onehundred twenty degrees.

As shown in FIGS. 7 and 8, the carrier 240 includes an output portion280 of the planetary gear assembly 144 and numerous retainers 292. Theoutput portion 280 is positioned within the internal cavity 276 definedby the sun gear 236 and within the internal cavity defined by the ringgear 232. The output portion 280 includes numerous splines 284 or otherconnection members that are configured to engage corresponding splinesformed on the shaft 146 (FIG. 4) to be driven by the drive system 108.The retainers 292 of the carrier 240 include protrusions 296, which arereceived by corresponding grooves formed in the posts 286 of the planetgears 244. The protrusions 296 interlock with the grooves to preventrotation of the posts 286 and to secure the planet gears 244 to thecarrier 240.

Reversibility of the Planetary Gear Assembly

The planetary gear assembly 144 is configured to be oriented in twopositions (orientations) relative to the rotor 140. As described abovewith reference to FIG. 4, the planetary gear assembly 144 is shown inthe first position in which the connection portion 252 of the ring gear232 is received by the opening 224 of the rotor 140, and the connectionportion 268 of the sun gear 236 is received by the opening 184 of thehousing 148. Accordingly, in the first position, the input torque member(i.e. the rotor 140) rotates directly the ring gear 232. The rotation ofthe ring gear 232 causes the planet gears 244 to rotate about theirrespective connection point to the carrier 240. Additionally, therotation of the ring gear 232 causes the planet gears 244 to revolvearound the central axis of the sun gear 236 and causes the carrier 240to rotate about the central axis of the sun gear 236. The sun gear 236,which is connected to the housing 148, has a fixed position and does notrotate in response to the rotation of the rotor 140.

With reference next to FIG. 9, the planetary gear assembly 144 is shownin the second position relative to the rotor 140. FIG. 9 is identical toFIG. 4 and includes all of the same parts. The only difference betweenFIG. 4 and FIG. 9 is that the planetary gear assembly 144 has been movedto the second position. In particular, the planetary gear assembly 144in FIG. 9 is identical to the planetary gear assembly of FIG. 4, but isshown in FIG. 9 in a reversed position (i.e. the second position)relative to the rotor. When the planetary gear assembly 144 is in thesecond position, the connection portion 268 of the sun gear 236 isreceived by the opening 224 of the rotor 140, and the connection portion252 of the ring gear 232 is received by the opening 184 of the housing148. In the second position, the rotor 140 directly rotates the sun gear236. The rotation of the sun gear 236 causes the planet gears 244 torotate about their respective connection point to the carrier 240.Additionally, the rotation of the sun gear 236 causes the planet gears244 to revolve around the central axis of the sun gear and causes thecarrier to rotate about the central axis of the sun gear. The ring gear232, which is connected to the housing 148, has a fixed position anddoes not rotate in response to the rotation of the rotor 140.

The flowchart of FIG. 10 illustrates an exemplary method 400 forarranging a gear train, such as the planetary gear assembly 144,relative to an input torque member, such as the rotor 140. In block 404,the method 400 provides the planetary gear assembly 144, which includesthe ring gear 232, the sun gear 236, the planet gears 244, and thecarrier 240. This refers to compiling the components of the planetarygear assembly 144 in a positionable unit. Thereafter, as shown in block408, the desired position of the planetary gear assembly 144 isselected. If the first position is selected, then, as in block 412, thering gear 232 is connected to the rotor 140. Next, the cover plate 156is connected to the bowl 152 of the housing 148, such that the sun gear236 is received by the opening 184. If the second position is selected,the sun gear 236 is connected to the rotor 140. Next, the cover plate156 is connected to the bowl 152 of the housing 148, such that the ringgear 232 is received by the opening 184.

The planetary gear assembly 144 may be moved between the first and thesecond positions. In particular, to change the position of the planetarygear assembly 144 a user first removes the cover plate 156. Next, theplanetary gear assembly 144 is moved away from the rotor 140 to rightalong the direction 288 to separate the planetary gear assembly from therotor. This movement separates one group of the splines 256, 272 on theplanetary gear assembly 144 from the splines 228 on the rotor 140.Thereafter, the planetary gear assembly 144 is oriented in the desiredposition. Next, the planetary gear assembly 144 is moved toward therotor 140 to the left along the direction 288 to connect the assembly tothe rotor in the desired position. This movement meshes the other groupof the splines 256, 272 on the planetary gear assembly 144 with thesplines 228 on the rotor 140. Next, the cover plate 156 is connected tothe bowl 152 of the housing 148 to secure the position of the planetarygear assembly 144.

Available Gear Ratios of the Electric Motor Assembly

The configurability of the planetary gear assembly 144 enables theelectric motor assembly 128 to generate a rotational output with aselectable gear ratio. Below, the available gear ratios for eachposition of the planetary gear assembly 144 are described. The differentgear ratios enable the planetary gear assembly 144 to multiply thetorque generated by the rotating rotor 140. Considering first thearrangement of FIG. 4, the planetary gear assembly 144 is shown in thefirst position with the shaft 146 connected to the output portion of thecarrier 240. In this arrangement, the ring gear 232 is connected to therotor 140 for rotation by the rotor, the carrier 240 is configured forrotation around the central axis of the sun gear 236, and the sun gearis fixed to the housing 148. Accordingly, in the first position, theplanetary gear assembly 144 introduces a first gear ratio between therotor 140 and the rotational output of the electric motor assembly 128,which, in this arrangement, is the output portion 280 (FIG. 5) of thecarrier 240. An exemplary first gear ratio in this arrangement is 1.6 to1 (rotation of rotor to rotation of carrier).

Considering now the arrangement shown in FIG. 9, the planetary gearassembly 144 is shown in the second position with shaft 146 still beingconnected to the output portion of the carrier 240. In this arrangement,the sun gear 236 is connected to the rotor 140 for rotation by therotor, the carrier 240 is configured for rotation about the central axisof the sun gear, and the ring gear 232 is fixed to the housing 148.Accordingly, in the second position, the planetary gear assembly 144introduces a second gear ratio between the rotor 140 and the outputportion 280 (FIG. 5) of the carrier 240. An exemplary gear ratio in thisarrangement is 2.7 to 1 (rotation of rotor to rotation of carrier).

It is noted that the same shaft 146 may be used in each of theabove-described two arrangements. Additionally, the position of theshaft 146 remains the same in each of the arrangements. Accordingly, theelectric motor assembly 128 is able to introduce two different gearratios between the rotor 140 and the shaft 146 with exactly the sameparts, only the relative position of the parts is changed.

As shown in FIG. 11, the planetary gear assembly 144 may be arranged togenerate another gear ratio when configured in the first position. Inthis third arrangement, the ring gear 232 is connected to the rotor 140for rotation by the rotor. The carrier 240 is fixed to the housing 148such that the planet gears 244 may rotate about the posts 286 (FIG. 6),but may not revolve around the central axis of the sun gear 236. Thecarrier 240 may be fixed to the housing 148 with any method, as known tothose of ordinary skill in the art. For example, as shown in FIG. 11,the carrier 240 may be fixed to the housing 148 with a fastening membersuch as post 270, which extends through the cover plate 156′ and isreceived by a corresponding opening in the carrier 240. Notably, the sungear 236 is received by the opening 184′ in the cover plate 156′, and isconfigured for rotation relative to the cover plate. Accordingly, thecover plate 156′ does not engage the splines 272 of the sun gear 236 andenables the sun gear to rotate relative to the housing 148. Therotational output member of the planetary gear assembly 144 is the sungear 236. To this end, a shaft 150 having a size different than theshaft 146 may be received by the sun gear 236 for rotation by the sungear. The shaft 150 may be connected to the sun gear 236 in a mannersimilar or identical to the manner in which the shaft 146 is connectedto the carrier 240. Therefore, in this arrangement, the planetary gearassembly 144 introduces a third gear ratio between the rotor 140 and therotational output of the electric motor assembly 128. It is noted thatan adapter member (not shown) may be provided such that the shaft 146(FIGS. 4 and 9) may be used with this arrangement (FIG. 11) of theplanetary gear assembly 144. The adapter may be positioned within thecavity defined by the sun gear 236.

As shown in FIG. 12, the planetary gear assembly 144 may be arranged togenerate yet another gear ratio (a fourth gear ratio considered thusfar) when configured in the second position. In this arrangement, thesun gear 236 is connected to the rotor 140 for rotation by the rotor.The carrier 240 is fixed to the housing 148 such that the planet gears244 may rotate about the posts 286 (FIG. 6), but may not revolve aroundthe central axis of the sun gear 236. Notably, the ring gear 232 isreceived by the opening 184′ in the cover plate 156′, and is configuredfor rotation relative to the cover plate. Accordingly, the cover plate156′ does not engage the splines 256 of the ring gear 232 and,therefore, enables the ring gear to rotate relative to the housing 148in response to rotation of the rotor 140. The rotational output of theplanetary gear assembly 144 is the ring gear 232. To this end, the shaft150 (also shown in FIG. 11) may be received by the ring gear 232 forrotation by the ring gear. Therefore, in this arrangement, the planetarygear assembly 144 introduces a fourth gear ratio between the rotor 140and the rotational output of the electric motor assembly 128. It isnoted that an adapter member (not shown) may be provided such that theshaft 146 (FIGS. 4 and 9) may be used with this arrangement (FIG. 12) ofthe planetary gear assembly 144. The adapter may be positioned withinthe cavity defined by the ring gear 232.

The planetary gear assembly 144 is configured to rotate an output shaftwith at least four different gear ratios depending on the position andthe configuration of the assembly. In at least some embodiments, a fifthoutput gear ratio of the planetary gear assembly 144 is also possible.In particular, a locked configuration may be achieved in which theoutput member of the planetary gear assembly 144 is rotated with a 1 to1 gear ratio (rotation of rotor to rotation of output). For example, alocked configuration may be achieved with the planetary gear assembly144 in the first position (FIG. 4) by connecting the carrier 240 to thering gear 232 and utilizing the carrier as the rotational output of theelectric motor assembly 128. Other locked configurations are possiblewith the planetary gear assembly 144 in the first and the secondpositions.

Compact Configuration of the Electric Motor Assembly

The position of the planetary gear assembly 144 relative to the stator136 and the rotor 140 enables the electric motor assembly 128 togenerate a comparatively high torque output from a compact package. Forexample, in a typical situation a planetary gear assembly is connectedto an output shaft of an electric motor. In this example, a total lengthof the combination is defined by the axial length of the electric motorplus the axial length of the planetary gear assembly. The electric motorassembly 128 serves to reduce the total length of the previouslydescribed combination. As used herein, the axial length of the planetarygear assembly 144 is a length of the planetary gear assembly measured inthe direction 288 of FIG. 4, and an axial length of the motor assembly128 may be determined by the distance between the line A and the line B(also of FIG. 4) as measured in the direction 288.

With reference again to FIG. 4, in contrast to the typical electricmotor and planetary gear assembly, the planetary gear assembly 144 doesnot contribute to the axial length of the electric motor assembly 128.For example, the planetary gear assembly 144 is positioned completelywithin the housing interior space (Lines A and B) and the statorinterior space (Lines C and D); thus, the planetary gear assembly 144does not contribute to the axial length of the motor assembly 128.Stated differently, the axial length of the planetary gear assembly 144overlaps completely with the axial length of the stator 136, thus it isthe axial length of the stator determines the axial length of the motorassembly 128.

The compact arrangement of the motor assembly 128 enables the componentsof the planetary gear assembly 144 to be positioned within the variousabove-described interior spaces. As shown in FIG. 4, in the firstposition the ring gear 232, the carrier 240, and the planet gears 244are positioned completely within the housing internal space (Lines A andB), the stator internal space (Lines C and D), and the rotor internalspace (Lines E and F). Whereas, the sun gear 236, is positionedcompletely within the housing internal space (Lines A and B) and thestator internal space (Lines C and D), and positioned partially withinthe rotor internal space (Lines E and F). As shown in FIG. 9, in thesecond position the sun gear 236, the carrier 240, and the planet gears244 are positioned completely within the housing internal space (Lines Aand B), the stator internal space (Lines C and D), and the rotorinternal space (Lines E and F). Whereas, the ring gear 232, ispositioned completely within the housing internal space (Lines A and B)and the stator internal space (Lines C and D), and positioned partiallywithin the rotor internal space (Lines E and F).

The electric motor assembly 128 described herein incorporates theplanetary gear assembly 144 within the housing, stator, and rotorinterior spaces such that the benefits of the planetary gear assembly(high torque output, among others) are realized without an increase inthe axial length of the motor assembly. For these reasons and others,the electric motor assembly 128 is useful in applications that requirean electric motor, which generates a large amount of torque, but thathas a small form factor, such as in hybrid vehicles and electricvehicles.

In another embodiment, (not illustrated) the planetary gear assembly 144contributes to the axial length of the electric motor assembly 128. Inthis embodiment, the axial length of the planetary gear assembly 144only partially overlaps with the axial length of the stator 136, suchthat the planetary gear assembly extends from the stator interior space.This extension from the stator interior space results in an increase inthe axial length of the motor assembly 128. For example, at least 50% ofthe axial length of the planetary gear assembly 144 is within the statorinterior space. In another example, at least 75% of the axial length ofthe planetary gear assembly 144 is within the stator interior space. Inyet another example, at least 90% of the axial length of the planetarygear assembly 144 is within the stator interior space. In each of theabove-described examples the housing interior space is also increased inresponse to the position of the planetary gear assembly 144. Theincrease in the housing interior space increases the length of thehousing in the direction 288.

Electric Traction Motor Configuration

As shown in FIG. 13, the electric motor assembly 128 may be configuredto function as an electric traction motor for the vehicle 100 in whichit is positioned. As the term is used herein, a traction motor generatesa drive torque for moving a vehicle. The electric motor assembly 128, inFIG. 13, is connected directly to the axle 124 to provide a drive torquefor the traction member 104 without a transmission element beinginterposed between the electric motor assembly and the axle.Accordingly, the wheel 116 and tire 120 rotate with the same angularvelocity as the output member of the planetary gear assembly 144. Alarge percentage of the torque generated by the electric motor assembly128 is transmitted directly to the wheel 116.

In operation, the drive system 108 rotates a portion of the tractionmember 104 in order to move the vehicle 100. Specifically, the speedcontroller 132 sends a signal to the winding 204 of the stator 136 whichcauses the rotor 140 to rotate with a particular angular velocity.Rotation of the rotor 140 causes the output member of the planetary gearassembly 144 to rotate. The rotation of the output member is coupleddirectly to the traction member 104 in order to move the vehicle 100.The drive system 108 is suitable for use with any type of vehicle 100including vehicles powered by both electric motors and internalcombustion engines, commonly referred to as “hybrid” vehicles as well asfully electric vehicles. Accordingly, in some embodiments the rotationaloutput of the drive system 108 may be coupled to the traction member 104via a transmission and/or a differential among other types of mechanicaltransmission devices.

As shown in FIG. 14, another embodiment of the vehicle 100′ includesnumerous drive systems 108′ each being associated with one of numeroustraction members 104′. The drive system 108′ and traction members 104′are positioned within a chassis 112′. In this embodiment, each tractionmember 104′ is independently driven and controlled by its associateddrive system 108′. One or more of the drive systems 108′ may beconfigured in a traction motor arrangement, as described above.

In another embodiment, as shown in FIG. 15, the chassis 112″ is anelement of a watercraft vehicle 100″. Exemplary watercrafts 100″ includeboats, personal watercraft, and the like. In this embodiment thetraction member 104″ assembly includes an axle 124″ and a propeller 292″configured to generate a traction force, which moves the watercraft 100″when rotated under water.

While the invention has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatother implementations and adaptations are possible. For example, variouschanges may be made and equivalent elements may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Also, there are advantages to individualadvancements described herein that may be obtained without incorporatingother aspects described herein. Therefore, it is intended that theinvention not be limited to the particular embodiment disclosed forcarrying out this invention, but that the invention will include allembodiments falling within the scope of the appended claims.

1. A planetary gear assembly comprising: a ring gear configured forconnection to a rotor of an electric motor when in a first position andconfigured for connection to a housing of the electric motor when in asecond position; a sun gear configured for connection to the housingwhen the ring gear is in the first position and configured forconnection to the rotor when the ring gear is in the second position;and a plurality of planet gears configured to mesh with the ring gearand the sun gear.
 2. The planetary gear assembly of claim 1 furthercomprising a carrier connected to the plurality of planet gears.
 3. Theplanetary gear assembly of claim 2 wherein an output portion of thecarrier is at least partially positioned within a cavity defined by thesun gear.
 4. The planetary gear assembly of claim 2 wherein the rotorrotates the carrier with a first gear ratio when the ring gear is in thefirst position, and the rotor rotates the carrier with a second gearratio when the ring gear is in the second position.
 5. The planetarygear assembly of claim 1 further comprising: a first splined portionprovided on the ring gear; a second splined portion provided on the sungear; a third splined portion provided on the rotor; and a fourthsplined portion provided on the housing, wherein (i) when the ring gearis in the first position the first splined portion meshes with the thirdsplined portion and the second splined portion meshes with the fourthsplined portion and (ii) when the ring gear is in the second positionthe first splined portion meshes the fourth splined portion and thesecond splined portion meshes with the third splined portion.
 6. Theplanetary gear assembly of claim 5 further comprising: a carrierconnected to the plurality of planet gears, the carrier including anoutput portion configured to provide a rotational output of the electricmotor.
 7. The planetary gear assembly of claim 6 wherein the housingdefines an interior space and the planets gears are positioned withinthe interior space.
 8. The planetary gear assembly of claim 6 whereinthe electric motor is a traction motor, and the traction motor ispositioned within a vehicle.
 9. An electric motor assembly comprising: ahousing; a stator positioned within the housing; a rotor positionedwithin the housing and configured to rotate relative to the stator; anda planetary gear assembly associated with the rotor, the planetary gearassembly comprising a ring gear, a sun gear, and a plurality of planetgears configured to engage meshingly the ring gear and the sun gear,wherein the planetary gear assembly is configured for positioning in afirst orientation in which the rotor rotates an output member of theplanetary gear assembly with a first gear ratio and in a secondorientation in which the rotor rotates the output member of theplanetary gear assembly with a second gear ratio.
 10. The electric motorassembly of claim 9 wherein in the first orientation the ring gear isconnected to the rotor and the sun gear is connected to the housing, andin the second orientation the ring gear is connected to the housing andthe sun gear is connected to the rotor.
 11. The electric motor assemblyof claim 9 further comprising a carrier connected to the plurality ofplanet gears, wherein the carrier is the output member of the planetarygear assembly in the first and the second orientations.
 12. The electricmotor assembly of claim 9 wherein: in the first orientation the ringgear is connected to the rotor, the sun gear is connected to thehousing, and the carrier is the output member of the planetary gearassembly, and in the second orientation the ring gear is connected tothe housing, the sun gear is connected to the rotor, and the carrier isthe output member of the planetary gear assembly.
 13. The electric motorassembly of claim 9 wherein: in the first orientation the output memberis the sun gear, and in the second orientation the output member is thering gear.
 14. The electric motor assembly of claim 9 wherein theplanetary gear assembly is oriented in a first direction defined alongan axis of rotation of the rotor when positioned in the firstorientation, and wherein the planetary gear assembly is oriented in asecond direction that is opposite the first direction when positioned inthe second orientation.
 15. The electric motor assembly of claim 9wherein the housing defines an interior space and the planetary gearassembly is positioned within the interior space.
 16. The electric motorassembly of claim 9 wherein the electric motor assembly is a tractionmotor, and the traction motor is positioned within a vehicle.
 17. Amethod for arranging a gear train relative to an input torque membercomprising: providing a planetary gear assembly comprising a ring gear,a sun gear, a plurality of planet gears, and a carrier for the planetgears, wherein at least two of the ring gear, sun gear, and carrier areconfigured to be connected to the input torque member such that aplurality of planetary gear configurations are possible for theplanetary gear assembly; selecting one of the plurality of planetarygear configurations for the planetary gear assembly; and arranging theplanetary gear assembly relative to the input torque member in theselected one of the plurality of planetary gear configurations.
 18. Themethod for arranging a gear train relative to an input torque member ofclaim 17 wherein the plurality of gear configurations includes a firstconfiguration wherein the ring gear is connected to the input torquemember.
 19. The method for arranging a gear train relative to an inputtorque member of claim 17 wherein the plurality of gear configurationsincludes a first configuration wherein the sun gear is connected to theinput torque member.
 20. The method for arranging a gear train relativeto an input torque member of claim 17 wherein the plurality of gearconfigurations includes at least four planetary gear configurations.